Image reading device comprising an outer peripheral member including two reference surfaces adjacent in the sub-scanning direction and differing in light reflectance

ABSTRACT

An outer peripheral member disposed at an outer periphery of a platen glass includes first and second reference surfaces. The first reference surface is a lower surface of an area extending along a side edge portion of the platen glass at an end in a main scanning direction. The second reference surface is located adjacent to the first reference surface in a second direction and differs in light reflectance from the first reference surface. An image processing portion determines whether outer periphery pixel data of an outer periphery area in line image data acquired successively while a scanning unit is moving, satisfies a border condition. A unit driving portion positions the scanning unit to a home position by moving the scanning unit a predetermined distance from where the scanning unit is located when it is determined that the outer periphery pixel data satisfies the border condition, and stops it.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority fromthe corresponding Japanese Patent Application No. 2020-155402 filed onSep. 16, 2020, the entire contents of which are incorporated herein byreference.

BACKGROUND

The present disclosure relates to an image reading device for reading animage from a document sheet placed on a platen glass.

An image reading device may have a function to execute a static documentsheet reading process. In the static document sheet reading process, animage is read from a document sheet placed on a platen glass. The staticdocument sheet reading process is often called an image reading processof a flat bed system.

In the static document sheet reading process, a unit driving portionmoves a scanning unit that includes a light emitting portion and a lightguide member that are formed along a main scanning direction, from apredetermined home position to an area below the platen glass.

The image reading device further includes an image sensor, an AFE(Analog Front End), and a data processing portion. The image sensorreceives light guided by the light guide member, and outputs a lineimage signal representing a light amount of the received light. The AFEconverts the line image signal to digital line image data that includesa plurality of pieces of pixel data. The data processing portionprocesses the line image data.

It is noted that the scanning unit may include a contact image sensorunit. The contact image sensor unit includes the light emitting portion,the light guide member being a condensing lens, and an image sensor of aCMOS type.

The home position is displaced from the area below the platen glass in asub scanning direction. While the scanning unit moves from the homeposition to the area below the platen glass, the moving speed of thescanning unit is stabilized.

Accordingly, the unit driving portion needs to position the scanningunit to the home position before the static document sheet readingprocess is executed.

There is known, for example, a configuration where a mark representingthe home position is formed on a reference plate for shading correction,and upon detecting the mark from the line image data, the dataprocessing portion detects that the scanning unit has reached the homeposition, wherein the reference plate is disposed adjacent to the platenglass.

SUMMARY

An image reading device according to an aspect of the present disclosureincludes a platen glass, an outer periphery member, a scanning unit, aunit driving portion, an image sensor, and an image processing portion.A document sheet is placed on the platen glass. The outer peripherymember is disposed at an outer periphery of the platen glass. Thescanning unit includes a light emitting portion and a light guide memberthat are formed along a main scanning direction, and moves below theplaten glass along a sub scanning direction that is perpendicular to themain scanning direction. The unit driving portion moves the scanningunit in a first direction or in a second direction, the first directionbeing along the sub scanning direction, the second direction beingopposite to the first direction. The image sensor receives light guidedby the light guide member and outputs a line image signal thatrepresents an amount of received light. The image processing portionprocesses line image data that includes a plurality of pieces of pixeldata corresponding to the line image signal. The outer peripheral memberincludes a first reference surface and a second reference surface. Thefirst reference surface is a lower surface of an area that extends alonga side edge portion of the platen glass at an end in the main scanningdirection. The second reference surface is located adjacent to the firstreference surface in the second direction and differs in lightreflectance from the first reference surface. The image processingportion executes a border determination process to determine whether ornot one or more pieces of outer periphery pixel data satisfy apredetermined border condition. The one or more pieces of outerperiphery pixel data are one or more pieces of pixel data of an outerperiphery area corresponding to the first reference surface or thesecond reference surface in the line image data acquired successivelywhile the scanning unit is moving from one of an area of the firstreference surface and an area of the second reference surface to theother in the sub scanning direction. The unit driving portion positionsthe scanning unit to a home position by causing the scanning unit tomove a predetermined distance in the second direction from a position atwhich the scanning unit is located when the image processing portiondetermines that the one or more pieces of outer periphery pixel datasatisfy the predetermined border condition, and causing the scanningunit to stop.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription with reference where appropriate to the accompanyingdrawings. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of an image reading device accordingto a first embodiment.

FIG. 2 is a configuration diagram of a CIS unit in the image readingdevice according to the first embodiment.

FIG. 3 is a block diagram showing a configuration of a user interfaceand a data processing device in the image reading device according tothe first embodiment.

FIG. 4 is a block diagram showing a configuration of a processing modulein a CPU of the image reading device according to the first embodiment.

FIG. 5 is a bottom diagram of a main body top plate portion in the imagereading device according to the first embodiment.

FIG. 6 is a flowchart showing an example of a procedure of a home returncontrol in the image reading device according to the first embodiment.

FIG. 7 is a configuration diagram of an image reading device accordingto a second embodiment.

FIG. 8 is a bottom diagram of a main body top plate portion in the imagereading device according to the second embodiment.

FIG. 9 is a configuration diagram of a scanning unit according to anapplication example of the image reading device according to anembodiment.

DETAILED DESCRIPTION

The following describes embodiments of the present disclosure withreference to the accompanying drawings. It should be noted that thefollowing embodiments are examples of specific embodiments of thepresent disclosure and should not limit the technical scope of thepresent disclosure.

FIRST EMBODIMENT: CONFIGURATION OF IMAGE READING DEVICE 1

An image reading device 1 according to a first embodiment executes animage reading process to read an image from a document sheet 9. Forexample, the image reading device 1 may be configured as a part of animage processing apparatus such as a copier, a facsimile apparatus, or amultifunction peripheral.

In the following description, the image read from the document sheet 9in the image reading process by the image reading device 1 is referredto as a read image.

In the present embodiment, the image reading device 1 includes a mainbody 101, a document sheet cover 102, a scanning unit 1 x, an AFE(Analog Front End) 14 x, a platen glass 16, and a moving mechanism 17(see FIG. 1).

The image reading device 1 further includes a user interface device 3and a data processing device 5.

The longitudinal direction of the scanning unit 1 x matches a mainscanning direction D1. The scanning unit 1 x includes a CIS (ContactImage Sensor) unit 140 and a carriage 100 that supports the CIS unit140.

In FIG. 1, a direction toward the depth direction of the paper surfaceis the main scanning direction D1, and a direction toward the right andleft of the paper surface is a sub scanning direction D2. The subscanning direction D2 is perpendicular to the main scanning directionD1.

The main body 101 is a housing storing the scanning unit 1 x and themoving mechanism 17. The platen glass 16 is disposed at an upper surfaceof the main body 101.

The moving mechanism 17 moves the scanning unit 1 x in the sub scanningdirection D2 in an area below the platen glass 16 and a white referencesurface 18 x that is described below. The moving mechanism 17 includes aunit support portion 17 a, a motor 17 b, a power transmission mechanism17 c, and a motor driving circuit 17 d.

The unit support portion 17 a supports the scanning unit 1 x so that thescanning unit 1 x can move in the sub scanning direction D2 in the areabelow the platen glass 16 and the white reference surface 18 x. Themotor 17 b is a drive source of a mechanism that moves the scanning unit1 x. The power transmission mechanism 17 c converts a rotational forceof the motor 17 b into a force along the sub scanning direction D2 andtransmits the force to the scanning unit 1 x.

When the motor 17 b rotates in a first rotation direction, the scanningunit 1 x moves in a first direction D21 along the sub scanning directionD2. When the motor 17 b rotates in a second rotation direction, thescanning unit 1 x moves in a second direction D22 that is opposite tothe first direction D21.

The motor driving circuit 17 d causes the scanning unit 1 x to move aspecified moving distance in the first direction D21 or the seconddirection D22 by controlling the direction and amount of rotation of themotor 17 b in accordance with a control command from the data processingdevice 5. The motor driving circuit 17 d is an example of a motorcontrol portion that controls the motor 17 b.

As shown in FIG. 2, the CIS unit 140 includes a light emitting portion11, a lens 13, and an image sensor 14. The light emitting portion 11,the lens 13, and the image sensor 14 are formed to extend along the mainscanning direction D1. That is, the longitudinal direction of each ofthe light emitting portion 11, the lens 13, and the image sensor 14matches the main scanning direction D1.

The light emitting portion 11 emits light upward. Specifically, thelight emitting portion 11 emits light toward the document sheet 9 placedon the platen glass 16.

The light emitted from the light emitting portion 11 reflects on thedocument sheet 9. For example, the light emitting portion 11 is an LEDarray that includes a plurality of LEDs arranged in alignment along themain scanning direction D1. In addition, the light emitting portion 11may include a light source and a light guide glass that guides lightfrom the light source in the main scanning direction D1, while causingthe light to irradiate upward.

The lens 13 is a condensing lens that guides a reflection light of thelight emitted from the light emitting portion 11, to the image sensor14. The reflection light is light that has diffused and reflected on thedocument sheet 9 or the white reference surface 18 x that is describedbelow.

The image sensor 14 receives the reflection light and detects a lightamount of the reflection light. Furthermore, the image sensor 14 outputsa line image signal Ia0 representing the detected light amount of thereflection light, to the AFE 14 x.

In the present embodiment, the image sensor 14 is a line sensor of aCMOS type. The lens 13 is an example of a light guide member that guidesthe reflection light to the image sensor 14.

The AFE 14 x converts analog line image signal Ia0 to digital line imagedata Id0, and outputs the line image data Id0 to the data processingdevice 5. The line image data Id0 includes a plurality of pieces ofpixel data of one line in the main scanning direction D1.

The line image data Id0 of a plurality of lines corresponding to onepage of the document sheet 9 is data of the read image corresponding toone page of the document sheet 9.

The image sensor 14 reads an image of the document sheet 9 as a colorimage. Accordingly, data of the read image is data of a color imagerepresenting the light amount of the reflection light for each of thecolors, red, green, and blue.

In the present embodiment, the light emitting portion 11 includes a redlight emitting portion 11R, a green light emitting portion 11G, and ablue light emitting portion 11B that respectively emit red light, greenlight, and blue light. In addition, the line image data Id0 of the threecolors that is acquired when the red light emitting portion 11R, thegreen light emitting portion 11G, and the blue light emitting portion11B emit light in sequence, constitutes the data of the read image.

The document sheet cover 102 is supported in such a way as to be openedand closed between a closing position for covering the upper surface ofthe platen glass 16 and an opening position for opening the uppersurface of the platen glass 16.

The image reading device 1 is configured to execute a static documentsheet reading process. The static document sheet reading process isoften called an image reading process of a flat bed system.

In the static document sheet reading process, the moving mechanism 17moves the scanning unit 1 x to read an image from the document sheet 9placed on the platen glass 16.

As shown in FIG. 3, the user interface device 3 includes an operationdevice 3 a and a display device 3 b. The operation device 3 a isconfigured to receive human operations, and includes, for example,operation buttons and a touch panel.

The display device 3 b includes a display panel such as a liquid crystalpanel configured to display an image and other information. It is notedthat the human operations include an operation by a human hand, as wellas an operation by a human voice and an operation by human line ofsight.

The data processing device 5 includes a CPU (Central Processing Unit)51, a RAM 52, a secondary storage device 53, a first communicationdevice 54, and a second communication device 55.

The secondary storage device 53 is a computer-readable, nonvolatilestorage device. The secondary storage device 53 is configured to storecomputer programs and various types of data. For example, either or bothof an SSD (Solid State Drive) and a hard disk drive are adopted as thesecondary storage device 53.

The CPU 51 is a processor configured to perform various types of dataprocessing and control by executing the computer programs stored in thesecondary storage device 53. It is noted that another processor, such asthe DSP, may perform the data processing and control in place of the CPU51.

The RAM 52 is a computer-readable volatile storage device. The RAM 52 isaccessed by the CPU 51. The RAM 52 primarily stores: data that is atarget of processing executed by the CPU 51; and data that is generatedby the CPU 51. The RAM 52 has a faster data access speed than thesecondary storage device 53.

The CPU 51 is configured to communicate with a host apparatus (notshown) that is an external apparatus, via a network such as a LAN (LocalArea Network). The host apparatus is a computer configured tocommunicate with the image reading device 1.

The first communication device 54 is an interface device configured torelay a signal transmission or a data communication performed betweenthe CPU 51 and another device included in the image reading device 1.For example, the CPU 51 transmits a control command to the motor drivingcircuit 17 d via the first communication device 54. In addition, the CPU51 acquires the line image data Id0 from the AFE 14 x via the firstcommunication device 54.

The second communication device 55 is a communication interface deviceconfigured to perform a communication with the host apparatus via thenetwork. The CPU 51 performs data transmission and reception with thehost apparatus all via the second communication device 55.

For example, the CPU 51 transmits data of the read image acquired by theimage reading process, to the host apparatus via the secondcommunication device 55.

The CPU 51 includes a plurality of processing modules that are realizedby the execution of the computer programs. The plurality of processingmodules include a main control portion 5 a, a reading control portion 5b, and an image processing portion 5 c (see FIG. 4).

The main control portion 5 a monitors mainly operations performed on theoperation device 3 a and data receptions performed by the secondcommunication device 55, and upon detection of an operation or a datareception, performs a control to start a process in accordance with thedetected operation or data reception.

The reading control portion 5 b causes the image reading device 1 toexecute the image reading process by controlling an ADF 15, the motordriving circuit 17 d, and the CIS unit 140. The image processing portion5 c executes various types of processes on the line image data Id0 thatis acquired in the image reading process. The image processing portion 5c is an example of a data processing portion that processes the lineimage data Id0 including a plurality of pieces of pixel datacorresponding to the line image signal Ia0.

The reading control portion 5 b controls the motor driving circuit 17 dto move and stop the scanning unit 1 x at a predetermined home positionP1. The home position P1 is an initial position of the scanning unit 1x, and is located on the second direction D22 side with respect to theplaten glass 16.

The reading control portion 5 b executes a static document sheet readingcontrol upon detection of a predetermined scan start operation performedon the operation device 3 a.

In the static document sheet reading control, the reading controlportion 5 b causes the moving mechanism 17 and the CIS unit 140 toexecute the static document sheet reading process.

In the static document sheet reading control, the reading controlportion 5 b controls the motor driving circuit 17 d to move the scanningunit 1 x from the home position P1 in the first direction D21.Furthermore, when the scanning unit 1 x is moving below the platen glass16, the reading control portion 5 b causes the CIS unit 140 to executethe image reading process.

The image reading device 1 includes an outer periphery member 18disposed at the outer periphery of the platen glass 16 (see FIG. 1, FIG.5).

The outer periphery member 18 includes the uniform white referencesurface 18 x that is a lower surface of an area of the outer peripherymember 18 located adjacent to the platen glass 16 in the seconddirection D22 (see FIG. 1, FIG. 5). The white reference surface 18 x isa lower surface of a portion of the outer periphery member 18 locatedadjacent to the platen glass 16 in the second direction D22.

The white reference surface 18 x is a uniformly colored surface having ahigh diffuse reflectance. For example, the white reference surface 18 xis a uniform white surface.

The image processing portion 5 c of the CPU 51 performs a shadingcorrection by using a piece of line image data Id0 that is acquired whenthe scanning unit 1 x faces the white reference surface 18 x. Theshading correction is a process to set a correction coefficient for theline image data Id0.

In the present embodiment, the scanning unit 1 x faces the whitereference surface 18 x when the scanning unit 1 x is located at the homeposition P1. The reading control portion 5 b moves the scanning unit 1 xfrom the home position P1 in the first direction D21, and at a timingwhen the scanning unit 1 x has moved a predetermined run-up distance,causes the CIS unit 140 to start the image reading process.

The run-up distance is a distance between the home position P1 and aposition corresponding to an edge of the document sheet 9 placed on theplaten glass 16. While the scanning unit 1 x moves the run-up distancefrom the home position P1, the moving speed of the scanning unit 1 x isstabilized.

The reading control portion 5 b causes the scanning unit 1 x to move inthe first direction D21 a distance that is a total of the run-updistance and a length of the document sheet 9 placed on the platen glass16. Thereafter, the reading control portion 5 b causes the CIS unit 140to end the image reading process, and causes the scanning unit 1 x tomove in the second direction D22 to the home position P1.

In the following description, a portion of the outer periphery member 18on which the white reference surface 18 x is formed, is referred to as areference plate.

Meanwhile, as a reference example, a mark representing the home positionP1 may be formed on the reference plate for shading correction, whereinthe reference plate is located adjacent to the platen glass 16. In thereference example, upon detecting the mark from the line image data Id0,the image processing portion 5 c detects that the scanning unit 1 x hasreached the home position P1.

On the other hand, it is desired that the shading correction isperformed in a state where the scanning unit 1 x is located at the homeposition P1, or performed while the scanning unit 1 x is moving from thehome position P1 toward the area below the platen glass 16. This makesit possible to perform the shading correction efficiently when thestatic document sheet reading process is executed.

In the present embodiment, the image processing portion 5 c performs theshading correction by using the line image data Id0 that is acquiredwhile the scanning unit 1 x is moving the run-up distance from the homeposition P1 in the first direction D21.

Accordingly, in a case where the mark representing the home position P1is formed on the reference plate, the home position P1 is set to aposition that is separated in the second direction D22 from the platenglass 16 more than the white area for shading correction in thereference plate is. This increases the time between the start ofmovement of the scanning unit 1 x from the home position P1 and thestart of reading an image from the document sheet 9 on the platen glass16, thereby increasing the processing time of the static document sheetreading process.

In addition, due to the increase in number of parts, it is notpreferable to have a dedicated sensor to detect the scanning unit 1 xthat has reached the home position P1.

The following describes a configuration for positioning the scanningunit 1 x to the home position P1 in the image reading device 1.

FIG. 5 is a bottom diagram of a main body top plate portion thatincludes the platen glass 16 and the outer periphery member 18.

As shown in FIG. 5, the outer periphery member 18 includes a firstreference surface 18 a and a second reference surface 18 b. The firstreference surface 18 a is a lower surface of an area that extends alonga side edge portion of the platen glass 16 at an end in the mainscanning direction D1. The second reference surface 18 b is a surfacelocated adjacent to the first reference surface 18 a in the seconddirection D22.

The second reference surface 18 b differs in light diffuse reflectancefrom the first reference surface 18 a. In the present embodiment, thesecond reference surface 18 b has a higher light diffuse reflectancethan the first reference surface 18 a. In other words, the firstreference surface 18 a has a lower light diffuse reflectance than thesecond reference surface 18 b.

For example, one of the first reference surface 18 a and the secondreference surface 18 b may be a black surface, and the other may be awhite surface. In this way, it is desirable that the first referencesurface 18 a and the second reference surface 18 b have a largedifference in light diffuse reflectance.

In addition, as shown in FIG. 5, it is desirable that a border linebetween the first reference surface 18 a and the second referencesurface 18 b is a straight line along the main scanning direction D1.

In the following description, an area in which the image of the documentsheet 9 is read in the main scanning direction D1 is referred to as areading target area A1, and an area occupied by the first referencesurface 18 a or the second reference surface 18 b in the main scanningdirection D1 is referred to as an outer periphery area A2 (see FIG. 5).

In the present embodiment, the white reference surface 18 x is a uniformsurface extending along the platen glass 16 and the total length of thereading target area A1 and the outer periphery area A2 in the mainscanning direction D1. In addition, a portion of the white referencesurface 18 x corresponding to the outer periphery area A2 is the secondreference surface 18 b. Accordingly, the second reference surface 18 bis a white surface. In this case, it is preferable that the firstreference surface 18 a is a black surface.

The light emitting portion 11, the lens 13, and the image sensor 14 areformed to extend along the length of the reading target area A1 and theouter periphery area A2 in the main scanning direction D1. In thepresent embodiment, the light emitting portion 11 and the lens 13 aredisposed in such a way as to extend out, with respect to the platenglass 16, longer toward the outer periphery area A2 than toward theopposite side in the main scanning direction D1 (see FIG. 5). It isnoted that the image sensor 14 is disposed in a similar manner.

The image sensor 14 outputs the line image signal Ia0 corresponding tothe reading target area A1 and the outer periphery area A2. In addition,the line image data Id0 includes a plurality of pieces of pixel data ofthe reading target area A1, and one or more pieces of pixel data of theouter periphery area A2.

The moving range of the scanning unit 1 x in the second direction D22 islimited to a range where the scanning unit 1 x faces the white referencesurface 18 x. Furthermore, the moving range of the scanning unit 1 x inthe first direction D21 is limited to a range where the scanning unit 1x faces the platen glass 16 and the first reference surface 18 a. Thatis, the moving range of the scanning unit 1 x is limited to a rangewhere the scanning unit 1 x faces at least one of the first referencesurface 18 a and the second reference surface 18 b.

[Home Return Control]

Next, an example of the procedure of a home return control is describedwith reference to the flowchart shown in FIG. 6.

The reading control portion 5 b and the image processing portion 5 cexecute the home return control upon occurrence of a predeterminedreturn start event. In the home return control, the scanning unit 1 x ismoved to the home position P1.

The return start event occurs when the image reading device 1 isstarted, when a movement of the scanning unit 1 x in the first directionD21 ends in the static document sheet reading process, or when aconveyed document sheet reading process ends.

In the following description, S1, S2, . . . are identification signsrepresenting a plurality of steps of the home return control. In thehome return control, first the reading control portion 5 b starts theprocess of step S1.

<Step S1>

In step S1, the reading control portion 5 b causes the light emittingportion 11 and the image sensor 14 to execute the line image readingprocess, and the image processing portion 5 c acquires, from the AFE 14x, the line image data Id0 that is acquired in the line image readingprocess.

In the line image reading process, the reading control portion 5 bcauses the light emitting portion 11 to emit light, and causes the imagesensor 14 to operate. For example, in the line image reading process,the reading control portion 5 b causes one or more of the red lightemitting portion 11R, the green light emitting portion 11G, and the bluelight emitting portion 11B to emit light.

Furthermore, in step S1, the image processing portion 5 c determineswhether or not an outer periphery pixel value is higher than apredetermined threshold value, wherein the outer periphery pixel valueis a value of outer periphery pixel data. The outer periphery pixel datais the one or more pieces of pixel data of the outer periphery area A2in the line image data Id0 acquired in the line image reading process.

In a case where the line image data Id0 includes a plurality of piecesof outer periphery pixel data, the outer periphery pixel value is arepresentative value of the plurality of pieces of outer periphery pixeldata. For example, the representative value is an average value or amaximum value.

Upon determining that the outer periphery pixel value is higher than thethreshold value, the image processing portion 5 c moves the process tostep S2. Otherwise, the image processing portion 5 c moves the processto step S5.

When the outer periphery pixel value is higher than the threshold value,the scanning unit 1 x is located to face the second reference surface 18b, and when the outer periphery pixel value is lower than the thresholdvalue, the scanning unit 1 x is located to face the first referencesurface 18 a.

That is, the image processing portion 5 c determines which of the firstreference surface 18 a or the second reference surface 18 b the scanningunit 1 x is located to face, by comparing the outer periphery pixelvalue with the predetermined threshold value.

<step S2>

In step S2, the reading control portion 5 b causes the image sensor 14to execute the line image reading process successively while causing thescanning unit 1 x to move in the first direction D21. Furthermore, theimage processing portion 5 c executes the process of step S3 while thescanning unit 1 x is moving.

<Step S3>

In step S3, the image processing portion 5 c determines, for each of aplurality of pieces of line image data Id0 that are acquiredsuccessively while the scanning unit 1 x is moving in the firstdirection D21, whether or not the outer periphery pixel value is equalto or lower than the threshold value.

The process of step S3 is repeated until it is determined that the outerperiphery pixel value is equal to or lower than the threshold value.When it is determined that the outer periphery pixel value is equal toor lower than the threshold value, the scanning unit 1 x has moved to aposition where it faces the first reference surface 18 a.

Upon determining that the outer periphery pixel value is equal to orlower than the threshold value, the image processing portion 5 c movesthe process to step S4.

When it is determined in step S3 that the outer periphery pixel value isequal to or lower than the threshold value, the scanning unit 1 x islocated at a border position P2 where it faces a border between thefirst reference surface 18 a and the second reference surface 18 b (seeFIG. 5).

<Step S4>

In step S4, the reading control portion 5 b causes the scanning unit 1 xto move a first specific distance in the first direction D21 from aposition at which the scanning unit 1 x is located when it is determinedthat the outer periphery pixel value is equal to or lower than thethreshold value, and stops the scanning unit 1 x. Thereafter, thereading control portion 5 b moves the process to step S5.

The process of step S4 causes the scanning unit 1 x to stop at aposition that is separated by the first specific distance from theborder position P2 in the first direction D21.

<Step S5>

In step S5, the reading control portion 5 b causes the image sensor 14to execute the line image reading process successively while causing thescanning unit 1 x to move in the second direction D22. Furthermore, theimage processing portion 5 c executes the process of step S6 while thescanning unit 1 x is moving.

<Step S6>

In step S6, the image processing portion 5 c determines, for each of aplurality of pieces of line image data Id0 that are acquiredsuccessively while the scanning unit 1 x is moving in the seconddirection D22, whether or not the outer periphery pixel value is higherthan the threshold value.

The process of step S6 is repeated until it is determined that the outerperiphery pixel value is higher than the threshold value. When it isdetermined that the outer periphery pixel value is higher than thethreshold value, the scanning unit 1 x is passing the border positionP2.

Upon determining that the outer periphery pixel value is higher than thethreshold value, the image processing portion 5 c moves the process tostep S7.

<Step S7>

In step S7, the reading control portion 5 b causes the scanning unit 1 xto move a second specific distance in the second direction D22 from aposition at which the scanning unit 1 x is located when it is determinedthat the outer periphery pixel value is higher than the threshold value,and causes the scanning unit 1 x to stop. The process of step S7 causesthe scanning unit 1 x to stop at the home position P1. Thereafter, thereading control portion 5 b ends the home return control.

As described above, the image processing portion 5 c executes theprocess of step S6 while the scanning unit 1 x is moving in the subscanning direction D2 from an area corresponding to the first referencesurface 18 a to an area corresponding to the second reference surface 18b. That is, the image processing portion 5 c executes the process ofstep S6 while the scanning unit 1 x is moving in the second directionD22.

The process of step S6 is a border determination process to determinewhether or not the outer periphery pixel data satisfies a predeterminedborder condition, the outer periphery pixel data being the one or morepieces of outer periphery pixel data of the outer periphery area A2 in aplurality of pieces of line image data Id0 that are acquiredsuccessively while the scanning unit 1 x is moving.

In the present embodiment, the border condition is a condition that theouter periphery pixel value is higher than the threshold value.

In addition, in step S7, the reading control portion 5 b and the movingmechanism 17 controlled by the reading control portion 5 b position thescanning unit 1 x to the home position P1 by moving the scanning unit 1x by a predetermined distance in the second direction D22 from aposition at which the scanning unit 1 x is located when it is determinedthat the outer periphery pixel data satisfies the border condition, andstopping the scanning unit 1 x.

In steps S6 and S7, when it is determined that the outer periphery pixeldata satisfies the border condition, the reading control portion 5 b andthe moving mechanism 17 cause the scanning unit 1 x to move to the homeposition P1 without stopping.

The reading control portion 5 b and the moving mechanism 17 that iscontrolled by the reading control portion 5 b, constitute an example ofa unit driving portion that causes the scanning unit 1 x to move in thefirst direction D21 or the second direction D22 along the sub scanningdirection D2.

With the adoption of the image reading device 1, it is possible, with asimple configuration, to position the scanning unit 1 x to the homeposition P1.

In addition, as described above, the moving range of the scanning unit 1x is limited to a range where the scanning unit 1 x faces at least oneof the first reference surface 18 a and the second reference surface 18b.

Accordingly, the image processing portion 5 c can easily determine whichof the first reference surface 18 a or the second reference surface 18 bthe scanning unit 1 x is located to face, by comparing the outerperiphery pixel value with the threshold value.

In the present embodiment, the motor 17 b is a stepping motor, and themotor driving circuit 17 d controls the rotation amount of the motor 17b by outputting a control pulse signal to the motor 17 b.

The control pulse signal is an example of a rotation pulse signal thatis output each time the motor 17 b rotates by a predetermined unitrotation amount. The motor driving circuit 17 d is an example of a pulseoutput circuit that outputs the rotation pulse signal.

In the present embodiment, a timing control circuit (not shown) outputs,in synchronization with the control pulse signal, a line synchronizationsignal to the image sensor 14. This allows the image sensor 14 to outputthe line image signal Ia0 in synchronization with the linesynchronization signal. That is, the image sensor 14 outputs the lineimage signal Ia0 at a timing synchronized with the control pulse signal.

In addition, in steps S4 and S7, the motor driving circuit 17 d stopsthe scanning unit 1 x when a predetermined target number of controlpulse signals have been output since an output of a control pulse signalcorresponding to a piece of outer periphery pixel data that wasdetermined to satisfy the border condition.

The target number in step S4 is the number of control pulse signalscorresponding to the first specific distance. The target number in stepS7 is the number of control pulse signals corresponding to the secondspecific distance.

With the configuration where the line synchronization signal is outputin synchronization with the control pulse signal, it is possible toposition the scanning unit 1 x to a target position with high accuracyin the home return control even in a case where the moving speed of thescanning unit 1 x is unstable.

It is noted that in a case where the line synchronization signal is notoutput in synchronization with the control pulse signal, the motordriving circuit 17 d causes the scanning unit 1 x to move the firstspecific distance or the second specific distance by controlling thetime period for which the scanning unit 1 x moves.

SECOND EMBODIMENT

Next, an image reading device 1A according to a second embodiment isdescribed with reference to FIG. 7 and FIG. 8. The following describesonly differences of the image reading device 1A from the image readingdevice 1.

Compared with the image reading device 1, the image reading device 1Aadditionally includes an ADF (Automatic Documents Feeder) 15 and acontact glass 16 a, and includes a white reference surface 18 y in placeof the white reference surface 18 x.

FIG. 8 is a bottom diagram of a main body top plate portion thatincludes the platen glass 16, the contact glass 16 a, and the outerperiphery member 18.

The contact glass 16 a is disposed in the reading target area A1 of theupper surface of the main body 101 to be adjacent to the white referencesurface 18 y in the second direction D22. The longitudinal direction ofthe contact glass 16 a matches the main scanning direction D1 (see FIG.8).

The document sheet cover 102 is supported in such a way as to be openedand closed between a closing position for covering the upper surfaces ofthe platen glass 16 and the contact glass 16 a, and an opening positionfor opening the upper surfaces of the platen glass 16 and the contactglass 16 a.

The moving mechanism 17 causes the scanning unit 1 x to move in the subscanning direction D2 in an area below the platen glass 16 and thecontact glass 16 a. In the present embodiment, the light emittingportion 11 emits light toward the document sheet 9 placed on the platenglass 16, or toward the document sheet 9 that passes over the contactglass 16 a.

The ADF 15 is built in the document sheet cover 102. In addition, aconveyance path 150 of the document sheet 9 is formed in the documentsheet cover 102. The conveyance path 150 is a path along which thedocument sheet 9 moves from a document sheet tray 151, passes over thecontact glass 16 a, and reaches a discharge tray 152.

The ADF 15 conveys, one by one along the conveyance path 150, aplurality of document sheets 9 placed on the document sheet tray 151,and discharges the document sheets 9 from the conveyance path 150 to thedischarge tray 152.

The image reading device 1A is configured to selectively execute thestatic document sheet reading process or the conveyed document sheetreading process. The conveyed document sheet reading process is oftencalled an image reading process of a document sheet feed system.

In the conveyed document sheet reading process, an image is read fromthe document sheet 9 conveyed by the ADF 15 in a state where thescanning unit 1 x is held at a static reading position P3 to face thecontact glass 16 a.

In the present embodiment, the home position P1 is located between theplaten glass 16 and the contact glass 16 a in the sub scanning directionD2.

The reading control portion 5 b executes a conveyed document sheetreading control or the static document sheet reading control when thescan start operation performed on the operation device 3 a is detected.The reading control portion 5 b executes the conveyed document sheetreading control in a case where a document sheet sensor (not shown)detects the document sheet 9 on the document sheet tray 151. Otherwise,the reading control portion 5 b executes the static document sheetreading control.

In the conveyed document sheet reading control, the reading controlportion 5 b controls the motor driving circuit 17 d to move the scanningunit 1 x from the home position P1 to the static reading position P3 andthen stop the scanning unit 1 x. Furthermore, the reading controlportion 5 b causes the ADF 15 to feed the documents 9 one by one andcauses the CIS unit 140 to execute the image reading process until thedocument sheet sensor does not detect the document 9 on the documentsheet tray 151.

In the image reading process, a process is repeated in which the lightemitting portion 11 emits light and the image sensor 14 detects thelight amount of the reflection light and outputs the line image signalIa0.

In the image reading device 1A, the outer periphery member 18 isdisposed at the outer periphery of the platen glass 16 and the contactglass 16 a (see FIG. 7, FIG. 8). A lower surface of a portion of theouter periphery member 18 between the platen glass 16 and the contactglass 16 a, is the white reference surface 18 y.

As is the case with the white reference surface 18 x, the whitereference surface 18 y includes a lower surface of a portion of theouter periphery member 18 between the platen glass 16 and the contactglass 16 a. Furthermore, the white reference surface 18 y is formed tocontinue from an area between the platen glass 16 and the contact glass16 a to an area that extends along a side edge portion of the contactglass 16 a at an end in the main scanning direction D1 in the outerperiphery area A2 of the lower surface of the outer periphery member 18.

In other words, the white reference surface 18 y is formed in the shapeof a letter L that is curved from the area between the platen glass 16and the contact glass 16 a to the area in the outer periphery area A2adjacent to the contact glass 16 a.

In the present embodiment, the moving range of the scanning unit 1 x inthe second direction D22 is limited to a range where the scanning unit 1x faces the contact glass 16 a. Furthermore, the moving range of thescanning unit 1 x in the first direction D21 is limited to a range wherethe scanning unit 1 x faces the platen glass 16.

Accordingly, in the present embodiment, too, the moving range of thescanning unit 1 x is limited to a range where the scanning unit 1 xfaces at least one of the first reference surface 18 a and the secondreference surface 18 b. With the adoption of the image reading device1A, a similar effect is obtained as in the case where the image readingdevice 1 is adopted.

FIRST APPLICATION EXAMPLE

The following describes a first application example of the image readingdevice 1 with reference to FIG. 9.

In the image reading device according to the first application example,the scanning unit 1 x of the image reading device 1 has been replacedwith a scanning unit 1 y shown in FIG. 9.

The scanning unit 1 y includes the light emitting portion 11, one ormore mirrors 12, the lens 13, an image sensor 14 a, and a carriage 100.The carriage 100 supports the light emitting portion 11, the mirrors 12,the lens 13, and the image sensor 14 a.

The mirrors 12 and the lens 13 are an example of a light guide memberthat guides the reflection light to the image sensor 14 a. The imagesensor 14 a is a line sensor of a CCD (Charge Coupled Device) type.

As is the case with the image sensor 14, the image sensor 14 a receivesthe light guided by the light guide member and outputs the line imagesignal Ia0 that represents an amount of the received light. With theadoption of the present application example, a similar effect isobtained as in the case where the image reading device 1 is adopted.

SECOND APPLICATION EXAMPLE

Next, a second application example of the image reading device 1 isdescribed. The present application example is an application example ofthe first application example.

In the present application example, the carriage 100 is divided into afirst carriage and a second carriage that have different moving speeds.The first carriage supports the light emitting portion 11 and a part ofa plurality of mirrors 12, and the second carriage supports theremaining part of the plurality of mirrors 12.

In addition, the lens 13 and the image sensor 14 a are fixed to theinside of the main body 101.

In addition, the mirrors 12 supported by the first carriage guide thelight reflected on the document sheet 9 to the mirrors supported by thesecond carriage, and the mirrors supported by the second carriage guidethe light to the lens 13 and the image sensor 14 a fixed to the insideof the main body 101. With the adoption of the present applicationexample, a similar effect is obtained as in the case where the firstapplication example is adopted.

THIRD APPLICATION EXAMPLE

Next, a third application example of the image reading device 1 isdescribed.

In the present application example, in step S4 of FIG. 6, the readingcontrol portion 5 b and the moving mechanism 17 execute the process ofstep S7, and then ends the home return control. In this case, in stepS3, the image processing portion 5 c executes the border determinationprocess while the scanning unit 1 x is moving in the first directionD21. In step S3, the border condition is a condition that the outerperiphery pixel value is equal to or higher than the threshold value.

Furthermore, the reading control portion 5 b and the moving mechanism 17reverse the moving direction of the scanning unit 1 x in the process ofstep S7 that is executed in step S4.

Subsequently, the reading control portion 5 b and the moving mechanism17 cause the scanning unit 1 x to move a predetermined distance in thesecond direction D22 from a position at which the scanning unit 1 x islocated when it is determined in step S3 that the outer periphery pixeldata satisfies the border condition, and cause the scanning unit 1 x tostop.

With the adoption of the present application example, a similar effectis obtained as in the case where the image reading device 1 is adopted.

It is to be understood that the embodiments herein are illustrative andnot restrictive, since the scope of the disclosure is defined by theappended claims rather than by the description preceding them, and allchanges that fall within metes and bounds of the claims, or equivalenceof such metes and bounds thereof are therefore intended to be embracedby the claims.

The invention claimed is:
 1. An image reading device comprising: aplaten glass on which a document sheet is placed; an outer peripherymember disposed at an outer periphery of the platen glass; a scanningunit including a light emitting portion and a light guide member thatare formed along a main scanning direction, and configured to move alonga sub scanning direction below the platen glass, the sub scanningdirection being perpendicular to the main scanning direction; a unitdriving portion configured to move the scanning unit in a firstdirection or in a second direction, the first direction being along thesub scanning direction, the second direction being opposite to the firstdirection; an image sensor configured to receive light guided by thelight guide member and output a line image signal that represents anamount of received light; and an image processing portion configured toprocess line image data that includes a plurality of pieces of pixeldata corresponding to the line image signal, wherein the outerperipheral member includes a first reference surface and a secondreference surface, the first reference surface is a lower surface of anarea that extends along a side edge portion of the platen glass at anend in the main scanning direction, the second reference surface islocated adjacent to the first reference surface in the second directionand differs in light reflectance from the first reference surface, theimage processing portion executes a border determination process todetermine whether or not one or more pieces of outer periphery pixeldata satisfy a predetermined border condition, the one or more pieces ofouter periphery pixel data are one or more pieces of pixel data of anouter periphery area corresponding to the first reference surface or thesecond reference surface in the line image data acquired successivelywhile the scanning unit is moving from one of an area of the firstreference surface and an area of the second reference surface to theother in the sub scanning direction, and the unit driving portionpositions the scanning unit to a home position by causing the scanningunit to move a predetermined distance in the second direction from aposition at which the scanning unit is located when the image processingportion determines that the one or more pieces of outer periphery pixeldata satisfy the predetermined border condition, and causing thescanning unit to stop.
 2. The image reading device according to claim 1,wherein the unit driving portion includes: a motor that is a drivesource; a pulse output circuit configured to output a rotation pulsesignal each time the motor rotates by a predetermined unit rotationamount; and a motor control portion configured to control the motor,wherein the image sensor outputs the line image signal at a timingsynchronized with the rotation pulse signal, and the motor controlportion stops the scanning unit when a predetermined number of rotationpulse signals have been output since an output of a rotation pulsesignal corresponding to a piece of outer periphery pixel data that wasdetermined to satisfy the border condition.
 3. The image reading deviceaccording to claim 1, wherein the outer periphery member includes auniform white reference surface that is a lower surface of an area ofthe outer periphery member located adjacent to the platen glass in thesecond direction, the white reference surface extending along a totallength of an area along the platen glass and the outer periphery area inthe main scanning direction, a portion of the white reference surfacecorresponding to the outer periphery area is the second referencesurface, and the image processing portion performs a shading correctionto set a correction coefficient for the line image data by using a pieceof line image data that is acquired when the scanning unit faces thewhite reference surface.
 4. The image reading device according to claim1, wherein the light emitting portion and the light guide member aredisposed in such a way as to extend out, with respect to the platenglass, longer toward the outer periphery area than toward a sideopposite to the outer periphery area in the main scanning direction. 5.The image reading device according to claim 1, wherein a moving range ofthe scanning unit is limited to a range where the scanning unit faces atleast one of the first reference surface and the second referencesurface.
 6. The image reading device according to claim 1, wherein theimage processing portion executes the border determination process whilethe scanning unit is moving in the second direction, and when it isdetermined that the outer periphery pixel data satisfies the bordercondition, the unit driving portion causes the scanning unit to move tothe home position without stopping.
 7. The image reading deviceaccording to claim 1, wherein the scanning unit includes a contact imagesensor unit that includes the light emitting portion, the light guidemember being a condensing lens, and the image sensor of a CMOS type.